How to tame hollow bass?

I have one of those Theatre In A Box 5-piece systems that came with good satellites but the sub is just too boomy and has a hollow sound, i.e not punchy. I stuffed some clothes into the sub's port and the bass seem a little tighter. Will I loose some frequencies by doing this? I know this being a sub/sat system the frequency range is not perfect, but I don't want to loose some of the music stuffs I want to hear.

All your doing is changing a bass reflex speaker to more like an acoustic suspension speaker. Altering the air pressure behind the woofer, thus it acts more like a spring. Not as efficient and thus would require more power to accomplish the same bass level. Shouldn't be a problem if your amp/receiver has enough reserve power without going into clipping or your sub amp can handle the extra power. My B&W speakers comes with plugs so you can plug the ports if you so chose and I haven't had any problems in doing that.
Just turn the volume up slower until your sure its not causing a problem.